MPE/iX Intrinsics Reference Manual (32650-90875)

Chapter 1 17

Introduction

What Is an Intrinsic Mechanism?

The MPE/iX intrinsics mechanism provides ﬂexible and convenient access to intrinsic

routines from various languages. When an external routine is designated as an intrinsic,

the compiler uses the intrinsics mechanism to determine how to invoke the routine

correctly. For example, a compiler receives information about the number of parameters,

the type of each parameter, and the functional return type (if applicable) and does the

following:

• Provides a consistent intrinsic interface

• Reduces the burden and error potential of coding multiple external procedure

declarations with all the parameters and type declarations required in some languages

• Ensures proper data type conversion

• Veriﬁes proper data alignment

• Provides proper indirect address references to data

• Generates proper reference parameter addresses

• Assigns values to default parameters and correctly resolves optional parameters

omitted at the end of an intrinsic call

• Provides parameter checking for languages that have no mechanism for detailed

external declarations

• Permits inter-language calls that may not be possible within a particular programming

language

• Provides name translation for case-insensitive languages

• Allows future extension without requiring source code changes

For example, Pascal/XL requires a detailed routine header for all external routines, and all

calls to a routine must adhere to strict typing constraints. However, by designating a

routine as an intrinsic, the compiler uses the intrinsics mechanism to determine how to

call the routine which permits removal of the detailed routine header and relaxes the strict

typing constraints.

Since the type information, stored in the intrinsic mechanism, is in language-independent

form, you can pass parameters of any type that conform functionally to the types expected

by the intrinsic. This allows convenient and ﬂexible access to system intrinsics through the

intrinsics mechanism.

NOTE

You can deﬁne routines for access as if they were intrinsics and place them in

new or existing intrinsic ﬁles and libraries.